1. Field of the Invention
The invention relates to a method for adaptive target processing in a vehicle radar. The targets in the surrounding environment are first detected by speed and location in the standard mode of the radar sensor. After detection of the targets in the standard mode the method switches to a precision mode, in which the distance measuring range of the radar sensor is adapted to the target surroundings detected in the standard mode.
2. Description of the Related Art
Usually the radar sensors used in automobiles are used for the control of speed in traffic surroundings such as country roads or highhways. The boundary or limiting conditions for such applications are such that information on the surroundings are necessary for a distance range of approximately 10 m to 150 m. However, for city traffic or stop-and-go traffic it is necessary to measure down to a short distance ahead of the vehicle ( less than 2 m).
In addition, there are specific traffic situations, e.g. two cars with nearly identical speed, in a passing maneuver in the detecting range of the radar antennas, in which the necessary target separation is not attained to a sufficient extent. Such cases require a secondary treatment, e.g. in a subsequent tracking filter. The tracking filter serves for tracking the single, individual targets detected by the radar device over time.
With radar systems the data cycle time, i.e. the time required for detecting the complete measuring range, is defined by the processing time for range finding (i.e. distance measurement) and Doppler measurement. With the popular systems for distance control in a vehicle this time is defined such that it meets the user requirements regarding accuracy of distance and speed measurement, while accepting the above-cited disadvantages.
The German patent publication DE 44 33 775 A1 discloses a method for adaptive target processing in a vehicle radar, which changes over between a normal mode and a precision mode with an extended resolution with regard to the distance.
It is an object of the invention to introduce an adaptive signal processing before the tracking filter, which makes it possible to cover the very short range just ahead of the antenna and to further improve the target separation.
This object is attained by the method according to the invention for adaptive target processing in a vehicle radar, in which the targets in the surrounding environment are detected by speed and location in the standard mode of the radar sensor, and then the method switches to a precision mode, in which the distance measuring range of the radar sensor is adapted to the target environment or surroundings detected in the standard mode.
In accordance with the present invention a precision mode with extended resolution and/or increased accuracy of measurement regarding speed and if necessary distance is introduced subsequent the above-described standard mode, in which the radar sensor detects targets by speed and distance with the resolution and measuring accuracy which is common for vehicle applications. Simultaneously, the distance measuring range of the radar is adapted to the target surroundings detected in the standard mode, i.e. in the precision mode merely a restricted distance measuring range is taken into consideration.
In case e.g. in the standard mode the detection shows a target or several targets in a given distance range, specifically this distance range can be detected within the precision mode and that with an extended speed resolution and/or speed measuring accuracy. In an advantageous embodiment in addition the distance resolution and/or the distance measuring accuracy can be increased.
Also cases are possible in which within the distance range adapted to the target surroundings merely the speed resolution and/or speed measuring accuracy is increased in the precision mode, the distance resolution and/or the distance measuring accuracy remaining constant.
In a particularly advantageous embodiment adaption of the distance measuring range while simultaneously increasing the resolution and/or measuring accuracy is performed in such manner that the data cycle time and thus the data renewal rate for the precision mode remains constant compared to the standard mode.
Consequently, the method according to the invention corresponds to the application of adaptive filters In signal processing, which filters may be adapted to the respective situation.
Thus an improved target separation and a very short range detection can be attained exclusively by altering the signal processing, without additional constructional measures being required at the radar sensor.